Diy helph


Hi,
Ive just put together an amp / preamp combo. Every thing sounds great but it has an audible hum when the amps input cables are connected to the preamps outs, the hum is not effected with the volume, its a set volume.
The weird thing is if i connect either a left or right channel only via the cable theres no hum?
Its only when both channels are connected.
Anyone got any ideas?
Regards
Mike
milo66
Agreed with @erik_squires that diyaudio is likely to be of more help with this issue.

Perhaps this thread is somewhere to start: https://www.diyaudio.com/forums/diyaudio-com-articles/163575-audio-component-grounding-interconnecti...

When dealing with ground loops it can be useful to just unplug everything and try to eliminate possible sources. Do you have to same issue if the pre is taken out of the loop? Do you have equipment plugged into multiple outlets? 

Good luck, ground loops can be a bitch...
Thanks for the info , I'm trying to eliminate an earth loop at the moment , rerouting the input leads inside amp to one side.
The title of this thread was a typo but I couldn't edit it for some reason.
Cheers
Mike
Nice one roxy54
All you can do is try every combo and it still might not go away. Move the pieces and IC around. I have a bag of iso transformers I try..
Start with in between.
Lotso luck.
have you try a ferrite ring on power cord of preamp and or amp close to the unit
Have you tried interchanging the cables? I had a situation where one of my cables potentially had damaged shielding and would catch radio interference when connected to my turntable.
At first I thought that the title of the thread was in a different language.
Nice one fuzztone, 
assuming that your connection is with rca's then most propably a ground is touching signal. Have you checked both cables or just one? What happens if you rock the rca's at pre's output or power's input while both cables are connected? Unscrew top covers-units off mains- and check that rca's at both units have a tight fit.
You can use a voltmeter to check any kind of shorting if you wish.
G